Again, this will be talking about Post-Roast Development and Cooling Time considerations depending on the ambient environment you are roasting in.

Ambient air temperature, batch size relative to the size of your cooling tray, humidity, and cleanliness are factors that can either be controlled or counteracted with knowledge and forethought.

Further descriptions of factors that will play in this and what to think about in relative to how combat negative effects.

Cleanliness.Whether you have a fixed or variable speed fan motor, how clean you keep all aspects of your airflow system will help or hinder the total cool down time of your coffee post discharge, regardless of ambient temperature, humidity or batch size. Ex. - A 20lb roast cooling in the tray of a machine which has been neglected and many parts of the airflow system covered in build-up, especially the impeller, could take just as long to cool down as a 40lb roast on the same machine which is clean. Meaning, a dirty machine can add from 30 seconds to over a minute longer, roasting in the same air conditions.

Batch size relative to the size of your cooling tray. The next thing to take in to account is the thought of how thick the bean mass is in the cooling tray. Depending on your style of roasted coffee being discharged from your roaster, it can range from 398 degrees F. to 460 degrees F., give or take some. The bean mass thickness relative to both width and fan power will affect the time it takes to cool down the complete roast. Also keep in mind temperature of the metal surfaces of the cooling tray, agitation arm, and walls will heat up, thus slowing the cool down time as well, especially as you are in a flow of back to back roasts.

Ambient temperature.With cleanliness and the batch size working for you, the next and greatest aspect to cool down time that can have an effect is the ambient temperature of air that is being drawn through the bean mass in the cooling tray. It could mean a difference of over 1 minute of cool down time from cold to hot ambient conditions. If you are updating your roast profiles season to season (Fall, Spring, Summer, Winter) for weather changes, (or to combat coffee aging, for example) there will be unseasonable day(s) every now and then. You must try to have the forethought to alter how you finish your roast of the current working profile, to keep to “cup profile”. If you are blessed with working in an environment where the air temperature is controlled or live in a climate that is pretty stable year round, you are a very fortunate minority!

Humidity.As a roaster, you know that moisture can be both your friend and enemy when it comes to the raw product. When it comes to the cooling time it is the same. Humidity is the enemy of coffee once roasted and as the degassing stage has ending, when it really has the ability to penetrate the bean. It is also the enemy of post discharge coffee as it is cooling down when the ambient air is hotter, yet works for you in cold ambient air conditions in cool down time. So from hot day to hot day, it will take longer to cool down and end the roasting process when the humidity is much higher, and vice versa for cold ambient temperatures.

So now the effects and how you may want to counteract them. While talking about this with another roaster, trying to explain the effects of each of the things mentioned, it was hard to talk about just one and how to use it to your benefit, for the sake of the coffee. EVERYTHING effects EVERYTHING. All of the aspects come into play.

The number one thing to take out of this is that you want the coffee to end roasting at the point where all possible flavor characteristics that your coffee’s flavor profile was developed for are achieved and how to keep any unwanted things from showing up in the cup.

So back to steak and eggs. Your coffee, like steak and eggs, will continue to roast once discharged from your roaster. The time it continues roasting will be affected by the effects mentioned above and the previous post. To be as generic and basic as possible, when the ambient conditions are hotter, the coffee will take longer to end roasting and when it is cooler it will end roasting quicker.

You have the ability to control at least two of the mentioned factors that can make a large impact, roaster cleanliness and batch size. As stated previously, keeping your roaster clean is a safety aspect that should always be well maintained. If kept clean it will have a positive impact on the flavor characteristics and a much larger ability to keep negative aspects from coming into development. The other thing you can have control over is batch size relative to cooling tray size. As you know, the less mass you have in your cooling tray the quicker it will cool, except for when there is not enough mass to cover the tray completely during agitation. It can be very helpful if you have the ability to roast only dedicated batch sizes. This will help out very much and ease the mind when working profiles. Ex. – If you only roast 2 sizes of batches, it will eliminate the extra variables when cupping, not only when developing, but also during production, creating and matching all flavor characters. If you were to roast many different batch sizes for a single coffee, you need to account for much more per roast on the cupping table, being not just end roasting time in the tray, but bean mass in the roaster drum and how it effects the roast. Though, like I mentioned, everything effects everything, and all factors need to be taken into thought.

Even those who do roast in an environment where you have a/c and heat to keep the ambient temperature at a steady level, you will need to still worry at times in regards to the humidity. Say you keep you roasting area at 68 degrees F. If the temperature were to fall below that, the a/c will not kick on and humidity can begin to rise. With that, you would not want to rely on a dehumidifier that can take out all extra and need moisture out of the air and especially out of the coffee.

Some Negative Effects and ideas of approach.

Let us say you start off creating a profile for a coffee in a normal, non-extreme ambient environment exactly as you/quality control/business owners have decided on your profile is locked in, and within your profile your post-crack development time is 15%. You created that with not accounting for the post discharge continued roasting. Then the weather/seasons change. Say you have a coffee that you develop in early, mild fall conditions, and the weather suddenly goes cold. Your coffee now once discharged will end roasting and cool quicker than when said profile was created. Now it is tasting a little underdeveloped from where it was previously. The acidity may be a little more pronounced but you have lost the body originally developed and a bit of woody, cereal, or bready note is showing through. To counteract this, one can extend the post crack development or further degree of temperature to counter the lack of post discharge continued development and cool down time. Taking this on the other extreme, you develop and create a coffee profile in the mild spring conditions and the weather/season changes. Here you may start to notice the coffee getting a little dryer, flavors characteristics are less prominent, roasty, baked, and acidity a little faded or sour. Now one can counter out this will a shorter post crack development or lower degree of temperature to counter the extended post discharge development and cool down time.

As AWLAYS, no two coffees are the same and should not be treated the so. There is no one method to counter act the post crack development relative to post discharge continued development. Maybe one coffee in the winter likes going a little longer in development time post crack prior to discharge, or opposite, same post crack development as originally profiled but reaching a further degree of temperature prior to discharge. Odds are it may be a little of each, slightly extended post crack and further in degree. This will be something you as the roaster will have to work with in order to achieve what the flavor profile coffee was originally set out to be.

As a roaster operator it is important to cup your roasts regularly and focus on how seasonal ambient environmental conditions are changing your end result in the cup. Try to take into thought when the profile was created for a “said” coffee and where it is now.

Again, having dictated/dedicated batch sizes for each coffee will eliminate some of the headache.

One more time, everything effects everything, so as temperatures swing, humidity rises and falls, and you are roasting different batch sizes, take all these into consideration. You can get ahead of all negative impacts and feel good with a product that will not only be good on the cupping table, but in the end consumer’s cup.